Nowadays, use is widely made of the hydraulic phase or camshaft adjuster, having an oscillating or rotary motor known from the field of hydraulics. Said oscillating motor phase adjuster is operated with engine oil pressure. The phase adjuster is conventionally situated on the ends of the camshaft in the power transmission path. The hydraulic camshaft adjuster is supplied with pressurized oil by means of the oil pump of the engine, Oil guiding ducts are provided in the camshaft for the supply to the actuator. By means of electronically controlled valves, the hydraulic oil is conveyed into the oil pressure chambers of the oscillating motor, and an adjustment of the phase position of the camshaft relative to the crankshaft is thereby attained. That side of the camshaft which faces toward the camshaft adjuster is mounted in a plain bearing on account of the hydraulic oil supply which is usually conducted through the camshaft. For the mounting of the camshaft at the end side, use is usually made of bushes or bearing blocks.
DE 100 02 512 A1 describes a cylinder head for a valve-controlled internal combustion engine, in which cylinder head are provided bearing seats for the inlet and outlet camshafts. On the side of the hydraulic camshaft adjuster, a bearing bush is provided in the bearing seat in order to compensate for the assembly recesses required in the bearing seat and to permit the supply of hydraulic oil to the camshaft adjuster in the bearing point. The hearing bush has two openings, which are arranged axially adjacent to one another, for the two-duct supply of oil to the camshaft adjuster, and a lubricant opening for the lubrication of the bearing point.
DE 10 2004 053 572 B4 describes a hydraulic camshaft adjuster having a two-duct oil guide in the camshaft. Two oil guiding ducts are provided within the camshaft, via which oil guiding ducts hydraulic oil is supplied to in each case one oil pressure chamber (depending on the desired adjusting direction). The oil guiding ducts extend through the camshaft and via external lines to an oil pump and an oil control valve.
DE 198 17 319 A1 describes a hydraulic camshaft adjuster in which a central control slide is provided in order to supply hydraulic oil to the working chambers of the vane-type adjuster. The central control slide replaces the external valve and is integrated, as a 4/2 directional control valve, into the central fastening screw for the camshaft, as a result of which only one radial oil guiding duct is required in the camshaft, and the axial structural length of the camshaft adjuster is reduced.
Various documents, such as for example DE 10 2005 059 841 A1 or DE 197 52 381 A1, are concerned inter alia with the lubrication of bearing points for camshafts.
Depending on the rotational speed range of the engine and the temperature, mechanical friction losses in the engine alone nowadays amount to up to 30 percent, and therefore account for a significant proportion of fuel consumption. The main sources of friction losses in the engine are the piston assemblies, the bearings of the engine shafts, and the valve drive components.
It is therefore the object of the invention to optimize a camshaft bearing point at the side of a hydraulic camshaft adjuster with regard to the occurring friction losses.